It would be desirable to provide for a more pleasant listening experience over a pair of headphones.
Preferably, the listening experience recreating the intended atmosphere of the original recording. In particular, preferred aspects of a pleasant listening experience include a feeling on the part of the listener that the sound is originating outside their head, or more particularly, that it is not coming from the headphones themselves. This effect is hereinafter denoted out of head (OOH). Further, and somewhat related, is the issue of naturalness in that a listener should ideally be able to close their eyes and be provided with a sense of being in a room with the performers or listening to an external set of speaker placed at a distance.
It is often the case that it is desirable to create a sense of a three dimensional surround sound environment to a headphone listener in any particular environment. For example, one popular form of environment for the utilization of headphones is on long aeroplane flights where, for example, in-flight movies or videos are shown.
Other popular uses of headphones is in a crowded environment where the listener wishes to adopt a private listening of the headphone signal while not disturbing those around the listener. It would be desirable to provide in such environments a means for providing full surround sound over headphones.
Unfortunately, when standard headphones are utilised, the out-of-head perception is lost and the sound appears to be coming from somewhere inside the listeners head and is substantially centralized.
Other sound formats face similar problems when reproduced over headphones. For example, the Dolby
AC-3 format, another popular format, is designed for the placement of a number of speakers around a listener so as to create a substantially richer sound environment. Again, when headphone devices are utilised in such an environment the intended spatial location of the sound is lost and again the sound appears to come from within the head of a listener.
The convolution of the audio signals with appropriate head related transfer functions (HRTFs) is known in the art. However, such full convolution techniques often require excessive computational resources and can not be readily implemented unless appropriate resources are made available.